We will examine mechanisms controlling the synthesis and processing of RNA virus nucleic acid and proteins in different kinds of mammalian cells in culture. We are studying devective interfering virus particles and their RNAs in vitro and in vivo to understand viral and cellular regulation of synthesis. Vesicular stomatitis virus and its T particles will be utilized as a model biochemical system for membrane viruses and findings from this system will be applied, where possible, to other viruses such as influenza virus, measles virus, and certain enteroviruses. Defective interfering viruses containing various sized segments of the virus genome will be employed in suitable RNA annealing experiments to map the virus genome and to prepare defined messenger RNA species for use in cell-free protein-synthesizing systems. Ultimately it should be feasible to assign the location virus genes coding for each virus specific protein. We still determine whether defective interfering particles can play a role in virus infection of living animals, (i.e., whether they slow the rate of virus spread in vivo, or influence the establishment of persistent infections), and whether they offer any potential for treatment, prophylaxis, or immunization against virus diseases.